Coronary artery disease is the leading cause of death within the United States for men and women. It is characterized by a buildup of material (often fatty) in the internal lumen of the coronary arteries. It is also associated with the hardening of the arterial walls. The buildup of material commonly starts on one side of the vessel and grows across the open lumen. As such, the last point of patency often occurs at the boundary between the material deposit (disease) and the healthy vessel.
Atherectomy is the process of removing diseased tissue from a stenosed lumen so as to restore patency and blood flow. There currently exist a number of devices that facilitate atherectomy. However, the operation of such devices has a number of shortcomings. In some instances, the active element of the atherectomy device acts equally in all directions, requiring the device to reside in the center of the diseased portion to maintain optimum efficacy. In other instances, the active element is directional but as such needs some method of visualization to orient the active element with respect to the diseased tissue. In many instances, the method of visualization that is employed is angiography, which is only capable of giving a silhouette of the open lumen.
Further, minimally invasive techniques for treating coronary artery disease, such as atherectomy, typically involve the placement of a guidewire through the occlusion prior to performing the atherectomy. For example, a chronic total occlusion (CTO) device can be used to place a guidewire through the occlusion and ultimately cross through the occlusion. Unfortunately, placement of the guidewire, while critical for effective treatment, may be difficult. In particular, when placing a guidewire across an occlusion, it may be difficult to pass the guidewire through the occlusion while avoiding damage to the artery. For example, it is often difficult to prevent the guidewire from directing out of the lumen into the adventitia and surrounding tissues, potentially damaging the vessel and preventing effective treatment of the occlusion.
Moreover, minimally invasive surgical procedures to treat coronary artery disease depend on the precise positioning and manipulation of interventional devices. Guidance provided by high-resolution imaging can enable the characterization of tissue and lesion properties in vivo prior to treatment. As the majority of atherogenesis occurs in an eccentric fashion within the artery, therapeutic tools that have onboard imaging provide a distinct opportunity to selectively treat the diseased portion of a vessel. Even with on-board imaging techniques, however, it can be difficult to interpret the images so as to properly orient and steer the interventional devices as needed.
Accordingly, there is a need for a consistent and precise mechanism for steering or orienting occlusion-crossing, atherectomy, or other interventional devices. The invention described herein is based on the novel realization that a characteristic morphology (or morphological structure) may be visualized when (or after) passing a structure through the lumen of a vessel containing an atherectomy plaque mass (atheroma).